The videos play smoothly on Premiere CS5, smoothly with only the occasional stutter on long track shots on WMV and VLC when compressed and streamed on Vimeo. However, on Youtube camera movement is very choppy on my computer. I have asked various people to watch the video both in Australia and overseas, with some finding it choppy like me and others saying it is smooth.

What could possibly be causing this? Is it something I'm doing wrong in my settings, if so what? Is this an issue with Adobe flash interacting with computers/Internet/video card? If so, can I change something in my settings to stop the issue? I've tried so many tests, with no success.

Video and test details below:

Original footage: Recorded from a video game with graphics settings on high as individual jpeg images at 120 fps, 1280x720, sound clips mostly 44100 with some higher/lower.
Original footage converted into uncompressed video with Lagarith codec on Virtualdub.
Premiere sequence settings: 59.94 fps, 1280x720, square pixels, progressive, 48000hz, stereo

I then have two copies that I encode using x264/AAC. One is a downloadable version at 59.94 fps, the other is downscaled to 29.97 fps for Youtube/Vimeo.